The invention relates to an oscillatory drive comprising a housing within which a drive shaft being rotatingly driven is arranged, an eccentric element driven by the drive shaft, and a tool drive shaft, wherein the eccentric element is coupled by means of a pivot element to a tool drive shaft for oscillatingly driving same about its longitudinal axis.
The invention further relates to a power tool comprising such an oscillatory drive.
Oscillatory drives have been used for many years, in particular, for performing special operations with power tools. For example, oscillatory drives are used in a variety of power tools for performing various grinding and polishing operations, cutting operations, e.g. for cutting out glass panes of windshields, for sawing, e.g. for sawing car body sheets and the like.
To this end relatively high power is necessary that must be transferred to the tool. Herein the efficiency of the oscillatory drive shall be as high as possible, while any noise emission shall be as small as possible. Also any vibrations possibly felt by the user of the tool shall be kept as small as possible.
From EP 0 372 376 A2 various designs of prior art oscillatory drives are known. An oscillatory drive as mentioned at the outset is known from U.S. Pat. No. 5,993,304.
According to the known device, an eccentric is driven by a rotating shaft. On the eccentric, a needle bearing is held that is guided between flat stop surfaces of a pivot lever by means of a crowned outer ring, the pivot lever thereby being oscillatingly driven.
However, these devices have a considerable noise emission and a low efficiency. Also a user may feel vibrations to a considerable extent, depending on the load to which the tool is subjected.
This arrangement suffers from the drawback that there is only a point like contact between the crowned outer ring of the needle bearing and the flat surfaces of the pivot lever affiliated therewith. Thereby, the power of the oscillatory drive is limited. Also a relatively high wear must be taken into account.